On a firm stand erect a three-inch soft wood board, a yard high and half
a yard broad, in which stand twenty deal rods. The longest should be
about five feet. The ones representing semi-tones should be painted a
different colour from the others, which can be left plain.
Rub the fingers in rosin-dust and set the rods vibrating with friction,
and you will have a manageable instrument, sweet and expressive.